Bought a couple of carnelian roughs off the Bay last year that were listed as "amazing old carnelian rough from chandler mt. Oregon". The color looked amazing in the photos - including what looked like cornflake/plume peeking out.

When I received them, I noticed that they both had a strangely uniform smooth tan skin. Hadn't seen this on Oregon carnelian before, but shrugged and tucked them away.

I ran across then today and the thought dawned on me that maybe they'd been heat treated. I put them in the saw and I believe my suspicions were confirmed. The red only penetrates a few mm and follows cracks. The inside is pale whitish agate.

I realize there are lots of natural agates that have an orangish/reddish exterior and pale interiors, but based I the weird color of the exterior and the dramatic color I believe these were likely heat treated.

Bought from a reputable seller - he may not have known as this might have been done a while ago.

It looks natural agate to me, too. Unfortunate that it didn't have a redder interior, but that's also characteristic of natural northwest carnelian agates - some have more red-orange inside, some less, than the outside reveals. There is some plume agate with carnelian colors in Chandler Mt. area agates, too (see photo below, which is old Moore Ranch).

All that said, I don't recall having seen pieces with a smooth brown side - almost looks like paint in your photos - though nearly anything's possible.

Put a half inch of sand in an oven proof container.Place stone on top of sand and cover with another half inch.Put in cold oven then:175°F Several hours (overnight is fine)275°F Four hours375°F Four hours475°F – 500°F Four hoursLeave in the oven overnight, without opening the door, or until pan is cold.

Some folks like togo to 550 F. You must remember that the color may not penetrate far into the stone. Carnelian beads in India were traditionally "burned" 5 times starting with the rough and ending with the burning of the finished bead or cab. The early burnings were not for color but to slightly soften the rough at each of the preforming stages. They have made carnelian beads for over 3,000 years and have made untold amounts. A lot of people soak the carnelian slabs in muriatic acid with iron nails in it for a month to add more iron to the quite porous agate. The Germans were very good at this and they dried the agates in a warm dry environment for 3 months before burning them to red.

What did you pay? want to buy some more? LOLI bought a milk crate over 1/2 full at an estate sale and got the same results cutting it.I think I paid $20.00 for it. was thinking about trying to heat treat it. But haven't wanted to burn up that much energy for a test run.

I should put it on eBay. Mybe I can get my $20.00 back?Naw I don't think I will stick someone else with it. I bought a piece of jade off of eBay one time and it turned out to be serpentine. I should of complained and returned itIt did make a nice 3" sphere

Looks typical of agate sitting out in the hot desert sun for a long time before someone found it. Almost everything in Arizona has the reddish coating, commonly called desert varnish.I have seen it on lots of material in SE Oregon. Not sure where the carnelian came from but it may be natural.

All the Brazilian carnelian rough I have bought has probably been baked also. 90% will have the outer color rind (1/2in deep is common) orange and the inside will be gray. There is 10% though that has orange all the way through.

So heated this way by mother nature or man? Who knows for sure except the people mining it.

Went out to my rock pile and pulled out a couple old pieces of rock that looked bake. I collected both of these so I know they are natural. The small piece is from the Owyhee's in eastern Oregon. The big piece comes from an area west of the Willow Creek jasper mine in Idaho. There was a lot of it and I thought I hit a home run until I cut some. It is all very boring inside and no sign of heat. It does not polish. ???? If this material got hot enough to melt the outside I do not think the inside could be as white as most of these pieces. It has a waxy feel to the skin. While it is hard on the outside it breaks pretty easy. I think the surface is just a natural finish that is mineral related, not heat. I do agree there is a lot of heated material out there. neal